Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
The no-argument constructor is a
requirement (tools like Hibernate use
reflection on this constructor to
instantiate objects).
I got this hand-wavy answer but could somebody explain further? Thanks
Hibernate, and code in general that creates objects via reflection use
Class<T>.newInstance()to create a new instance of your classes. This method requires a public no-arg constructor to be able to instantiate the object. For most use cases, providing a no-arg constructor is not a problem.There are hacks based on serialization that can work around not having a no-arg constructor, since serialization uses jvm magic to create objects without invoking the constructor. But this is not available across all VMs. For example, XStream can create instances of objects that don’t have a public no-arg constructor, but only by running in a so-called “enhanced” mode which is available only on certain VMs. (See the link for details.) Hibernate’s designers surely chose to maintain compatibility with all VMs and so avoids such tricks, and uses the officially supported reflection method
Class<T>.newInstance()requiring a no-arg constructor.